Enhanced optical path and electron diffusion length enable high-efficiency perovskite tandems

Abstract

Tandem solar cells involving metal-halide perovskite subcells offer routes to power conversion efficiencies (PCEs) that exceed the single-junction limit; however, reported PCE values for tandems have so far lain below their potential due to inefficient photon harvesting. Here we increase the optical path length in perovskite films by preserving smooth morphology while increasing thickness using a method we term boosted solvent extraction. Carrier collection in these filmsas madeis limited by an insufficient electron diffusion length; however, we further find that adding a Lewis base reduces the trap density and enhances the electron-diffusion length to 2.3 µm, enabling a 19% PCE for 1.63 eV semi-transparent perovskite cells having an average near-infrared transmittance of 85%. The perovskite top cell combined with solution-processed colloidal quantum dot:organic hybrid bottom cell leads to a PCE of 24%; while coupling the perovskite cell with a silicon bottom cell yields a PCE of 28.2%.

PbS Colloidal Quantum Dot Inks for Infrared Solar Cells

“…Finally, the PCE of the tandem solar cell reached 20.2%, exceeding 18% for the single-junction perovskite solar cells. Chen et al. (2020) increased the optical path length and electron diffusion length through boosting the solvent extraction techniques, and thereby further increasing the PCE of Cs 0.05 FA 0.81 MA 0.14 PbI 2.55 Br 0.45 perovskite top cell to ~19% ( Figure 8 D).…”

Spatial Distribution Recast for Organic Bulk Heterojunctions for High‐Performance All‐Inorganic Perovskite/Organic Integrated Solar Cells

“…[43] While the perovskite possesses an ambipolar charge transport property with both high hole and electron mobilities, which could efficiently extend diffusion length up to 1 µm with low charge carrier recombination rate. [44] Then all the generated electrons and holes in the corresponding perovskite and organic BHJ active layer transport toward anode and cathode, respectively, under the built-in electric field. During this process, the holes generated in the perovskite and the electrons generated in organic BHJ should pass through the ambipolar organic BHJ and perovskite films, [45] and the highest occupied molecular orbital (HOMO) of donor and LUMO of acceptor should match well with the E C and E V of perovskite film to warrant charge transportation through the device without barrier.…”

Recombination junctions for efficient monolithic perovskite-based tandem solar cells: physical principles, properties, processing and prospects

“…4 This success can largely be ascribed to the excellent optoelectronic properties of metal halide perovskites, such as a sharp and high onset of their absorption coefficient, a low Urbach energy, a tunable bandgap, long carrier diffusion length, and low nonradiative recombination rates of charge carriers. [5][6][7][8][9][10][11] These properties also make PSCs ideal candidates for the realization of tandem devices, coupled with established technologies such as crystalline silicon (c-Si) solar cells. 12,13 This is of high relevance as it opens a realistic route to overcome the practical single-junction PCE limit of c-Si, which is steadily approaching, even in mass manufacturing environments.…”